Is shadow matter?
Matter, in simplest terms, is defined as anything that occupies space and has mass. We see examples of matter all around us; trees, human beings, equipment, water, homes, food, etc., everything is matter.
In comparison, a shadow has neither mass nor does it occupy space. It is nothing but a phenomenon created by obstruction of light by an object (one that does not transmit light). A shadow moves with the object (that blocks the path of light) or the source of light. It does not displace anything in its path and hence does not occupy space. It does not have any mass, if it did, it would have caused visible (or noticeable) effects on the objects it falls on. Thus, a shadow can not be classified as matter.
Hope this helps.
First, let us understand what is matter. By definition, matter is anything that has mass and that occupies space. Examples of matter would be: air, water, soil, cheese, gasoline and so on.
Now, let us see what is meant by a shadow. A shadow is caused when an object obstructs the path of light. In other words, when an object is placed in the dark and a small source of light (as from a flashlight) falls on it, there is no scattering of light taking place. Because of this, we can see the shadow of the object behind it. Shadows are seen during eclipses.
Does the shadow have mass? Does it occupy space? The answers to both these questions is no. So a shadow is not matter.